// Copyright (c) 2018 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_INDEX_BLOCKFILTERINDEX_H
#define BITCOIN_INDEX_BLOCKFILTERINDEX_H

#include <blockfilter.h>
#include <chain.h>
#include <flatfile.h>
#include <index/base.h>
#include <util/hasher.h>

static const char *const DEFAULT_BLOCKFILTERINDEX = "0";

/** Interval between compact filter checkpoints. See BIP 157. */
static constexpr int CFCHECKPT_INTERVAL = 1000;

/**
 * BlockFilterIndex is used to store and retrieve block filters, hashes, and
 * headers for a range of blocks by height. An index is constructed for each
 * supported filter type with its own database (ie. filter data for different
 * types are stored in separate databases).
 *
 * This index is used to serve BIP 157 net requests.
 */
class BlockFilterIndex final : public BaseIndex {
private:
    BlockFilterType m_filter_type;
    std::unique_ptr<BaseIndex::DB> m_db;

    FlatFilePos m_next_filter_pos;
    std::unique_ptr<FlatFileSeq> m_filter_fileseq;

    bool ReadFilterFromDisk(const FlatFilePos &pos, BlockFilter &filter) const;
    size_t WriteFilterToDisk(FlatFilePos &pos, const BlockFilter &filter);

    Mutex m_cs_headers_cache;
    /**
     * Cache of block hash to filter header, to avoid disk access when
     * responding to getcfcheckpt.
     */
    std::unordered_map<BlockHash, uint256, FilterHeaderHasher>
        m_headers_cache GUARDED_BY(m_cs_headers_cache);

    bool AllowPrune() const override { return true; }

protected:
    bool CustomInit(const std::optional<interfaces::BlockKey> &block) override;

    bool CustomCommit(CDBBatch &batch) override;

    bool WriteBlock(const CBlock &block, const CBlockIndex *pindex) override;

    bool Rewind(const CBlockIndex *current_tip,
                const CBlockIndex *new_tip) override;

    BaseIndex::DB &GetDB() const override { return *m_db; }

public:
    /** Constructs the index, which becomes available to be queried. */
    explicit BlockFilterIndex(std::unique_ptr<interfaces::Chain> chain,
                              BlockFilterType filter_type, size_t n_cache_size,
                              bool f_memory = false, bool f_wipe = false);

    BlockFilterType GetFilterType() const { return m_filter_type; }

    /** Get a single filter by block. */
    bool LookupFilter(const CBlockIndex *block_index,
                      BlockFilter &filter_out) const;

    /** Get a single filter header by block. */
    bool LookupFilterHeader(const CBlockIndex *block_index, uint256 &header_out)
        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_headers_cache);

    /** Get a range of filters between two heights on a chain. */
    bool LookupFilterRange(int start_height, const CBlockIndex *stop_index,
                           std::vector<BlockFilter> &filters_out) const;

    /** Get a range of filter hashes between two heights on a chain. */
    bool LookupFilterHashRange(int start_height, const CBlockIndex *stop_index,
                               std::vector<uint256> &hashes_out) const;
};

/**
 * Get a block filter index by type. Returns nullptr if index has not been
 * initialized or was already destroyed.
 */
BlockFilterIndex *GetBlockFilterIndex(BlockFilterType filter_type);

/** Iterate over all running block filter indexes, invoking fn on each. */
void ForEachBlockFilterIndex(std::function<void(BlockFilterIndex &)> fn);

/**
 * Initialize a block filter index for the given type if one does not already
 * exist. Returns true if a new index is created and false if one has already
 * been initialized.
 */
bool InitBlockFilterIndex(
    std::function<std::unique_ptr<interfaces::Chain>()> make_chain,
    BlockFilterType filter_type, size_t n_cache_size, bool f_memory = false,
    bool f_wipe = false);

/**
 * Destroy the block filter index with the given type. Returns false if no such
 * index exists. This just releases the allocated memory and closes the database
 * connection, it does not delete the index data.
 */
bool DestroyBlockFilterIndex(BlockFilterType filter_type);

/** Destroy all open block filter indexes. */
void DestroyAllBlockFilterIndexes();

#endif // BITCOIN_INDEX_BLOCKFILTERINDEX_H
